In the manufacture of propylene homopolymers and copolymers, conventional polymerization techniques being unsupported catalyst result in the simultaneous production of substantial quantities of atactic polymer in addition to the desired product of high crystallinity and isotacticity. Various methods have been employed for the purification and separation of these two polymers. The by-product, i.e., the atactic polymer of low crystallinity is being utilized commercially as a component in various adhesive compositions, roofing materials, caulking compounds, etc.
Recently, developments have been made of new catalysts which are highly active and more stereospecific than the aforementioned conventional catalysts. The proportion of atactic polymer in the polymers produced employing these catalysts are substantially reduced and therefore the polymer product generally does not require any purification for removal of the atactic or low crystalline polymer. Because of the rapid adaptation of existing polymer facilities to the use of these new catalysts, there has been generated a serious shortage of low crystalline, atactic polymers.
In the prior art processes have been disclosed for the preparation of ethylene-propylene copolymers of low crystallinity. Thus, U.S. Pat. No. 3,951,935 to Englemann, No. 3,933,934 to Bailly et al. and No. 3,789,036 to Longi et al. as well as French Pat. No. 2,127,368 deal with direct polymerization of ethylene and propylene using titanium-based catalysts. U.S. Pat. No. 3,300,459 discloses the preparation of an ether extract of a vanadium-catalyzed ethylene-propylene copolymer. None of these copolymer products have the properties required of the novel polymers of this invention.
It is, therefore, an object of the present invention to provide a novel amorphous polymer of propylene and ethylene, having improved physical properties.